The invention relates to motion-picture cameras provided with a diaphragm control system capable of fade-out, fade-in and/or fadeover effects, of the type wherein decrease of diaphragm aperture performed for fade-out is always performed to the extent of a constant amount of diaphragm-setting change, with the diaphragm control system continuing to be capable of negative-feedback light-responsive diaphragm control even after the fade-out has been effected.